The double feature used to be a staple of New York repertory houses, and Film Forum is bringing it back. The “Summer Double Features” series, from Aug. 11 to Sept. 5, includes twenty-eight pairings, ranging from silents to independents, from European political fantasies to Hollywood extravaganzas. The Aug. 22 program offers two film-noir classics, both from 1949, about lovers on the run—Nicholas Ray’s first feature, “They Live by Night,” and Joseph H. Lewis’s “Gun Crazy,” a key inspiration for “Bonnie and Clyde.”